1. Field of the Invention
This invention relates generally to a method of making a bonded rubber-metal article with a laminated rubber member under compression, more particularly to vibration control devices with a laminated rubber member bonded between two rigid members, and specifically to a torsional vibration damper with annular laminated rubber member directly bonded to the inner and outer rigid or metal members and under compression.
2. Description of the Prior Art
As vehicle engine technology develops, engines are producing high drive torques and more demanding requirements on crankshaft dampers which have a rubber member connecting two rigid, for example metal, members. As a consequence, reliance on friction is not sufficient, and the rubber member must be bonded to the metal surfaces to sustain the high drive torque and improve the durability. Current approaches to bond the rubber to the metal include using a rubber-metal adhesive applied to the rigid or metal members for subsequent vulcanization bonding, or injection molding of a self-bonding rubber composition. These approaches generally permit the rubber to go into a state of tension upon cooling from the vulcanization temperature, resulting in decreased durability and premature part failures at low temperatures. To avoid rubber in tension and maintain the rubber in a state of compression, post-vulcanization bonding may be used with various rubber-metal adhesives applied to the metal bonding surfaces. These bonding technologies generally require a number of expensive process steps to prepare the metal and/or rubber surfaces for bonding, to apply adhesives, to deal with chemicals or emissions, and so forth. A two-step cure method has been disclosed in U.S. Pat. Nos. 7,078,104 and 7,291,241 which disclose self-bonding rubber formulations that eliminate conventional adhesives and a two-step cure method to form the rubber member and bond it to the metal, thus retaining some degree of compression on the rubber. However, in practice, given the competing constraints on formulating and processing the rubber to optimize a tradeoff between bonding and retained compression while tuning rubber modulus, damping, heat resistance, etc., it has yet proven difficult to retain sufficient compression to achieve desired durability targets for crankshaft dampers. The same concerns arise for any kind of bonded rubber composite article or part in which the rubber member is bonded between rigid members and held under compression to enhance durability.
What is needed is a process for bonding rubber to rigid parts with a greater degree of flexibility to achieve higher states of compression over the life of the composite part without sacrificing adhesion or any desired tuning of rubber properties and without using conventional adhesives with their demanding surface preparation requirements.
Mention is made of Applicant's U.S. Pat. No. 8,246,872 and U.S. Pat. No. 7,834,090.